References may be made to Journals “Biermann et al., Angew. Chem. Int. Ed. Year 2000, Vol. 39, pp. 2206-2224” and Seniha Gtiner et al., Prog. Polym. Sci. Year 2006, Vol. 31, pp. 633-670”, wherein use of fatty epoxides as plasticizers that are compatible with polyvinyl chloride (PVC) and as stabilizers for PVC resins to improve flexibility, elasticity and toughness and to impart stability of polymer towards heat and UV radiation was disclosed.
Today one of the most important epoxidized vegetable oils is epoxidized soybean oil. Its worldwide production is about 200,000 tons/year.
References may be made to U.S. Pat. No. 2,810,733 and U.S. Pat. No. 4,215,058 wherein epoxidation of vegetable oils is carried out with a mixture of formic acid/hydrogen peroxide or peracids. This process leads to high amount of waste, by-products. It also causes several concerns about safety and engenders corrosion problems that are interrelated to the percarboxylic acids used. More environmentally friendly and cleaner synthetic route than the non-ecofriendly conventional process is highly desirable.
References may be made to Journals “Orellana-Coca et al., J. Mol. Catal. B: Enzym., Year 2007, Vol. 44, pp. 133-137; Warwel and Klass J. Mol. Catal. B: Enzym., Year 1995, Vol. 1, pp. 29-35; Piazza et al., J. Mol. Catal. B: Enzym. Year 2003, Vol. 21, pp. 143-151” wherein immobilized enzymes (lipase, oat sead peroxygenase, etc.) exhibit good performance for this reaction but they are very sensitive to the kind of substrate employed and they are often not suitable for obtaining high yields in polyepoxidized products. Homogeneous catalysts including methyltrioxorhenium and peroxophosphotungstates (U.S. Pat. No. 5,430,161; Kozhevnikov et al., J. Mol. Catal. A: Chem., Year 1998, Vol. 134, pp. 223-228; Jiang et al., J. Am. Oil Chem. Soc., Year 2010, Vol. 87, pp. 83-91) show good catalytic activity with hydrogen peroxide as oxidant. Difficulty in catalyst separation and reuse are the issues with those homogeneous catalysts. Often, additional nitrogen-based co-catalysts (substituted imidazoles, pyridine, etc) need to be used along with the homogenous catalysts to obtain high conversion and epoxide selectivity.
Heterogeneous catalysts are advantageous as they can be separated easily from the reaction mixtures. Ti-grafted silica catalysts have been examined for the liquid phase oxidation of a mixture of fatty acid methyl esters. While these catalysts are active, they require very long reaction times (24 hr or more) and the epoxide yields are not as high as those obtained in the industrial processes (Rios et al., J. Catal. Year 2005, Vol. 232, pp. 19-26; Campanella et al., Green Chem. Year 2004, Vol. 4, pp. 330-334; Guidotti et al., J. Mol. Catal. A: Chem., Year 2006, Vol. 250, pp. 218-225; Guidotti et al., Catal. Lett. Year 2008, Vol. 122, pp. 53-56). Sol-gel prepared alumina catalyst showed efficient activity but again required long contact times (24 hr) to achieve 95% conversion of fatty acid methyl esters (Sepulveda et al., Appl. Catal. A: Gen., Year 2007, Vol. 318, pp. 213-217).
References may be made to Journal “Fat Sci. Technol., Year 1995, Vol. 97, pp. 269-273” wherein Debal et al reported the use of MoO3-t-butylhydroperoxide system for the epoxidation of methyl linoleate at 95-115° C. Besides the expected diepoxy derivates dihydroxy tetrahydrofurans were obtained and whose yield reaches up to 75%. The cause of the formation of such large amount of unwanted side products was explained due to the formation of molybdic acid from MoO3 and tert.-butyl hydroperoxide. While the MoO3 or Mo(CO)6-tert.-butyl hydroperoxide/cumylhydroperoxide system is efficient for epoxidation of monoenic fatty esters, it results in a complex mixture of products in the epoxidation of polyenic fatty esters (Debal et al., Lipid/Fett, Year 1993, Vol. 95 (Issue No. 6), pp. 236-239).
References may be made to U.S. Pat. No. 5,081,267, wherein epoxidation of olefinic compounds by reaction with an organic hydroperoxide in the presence of a solid, heterogeneous catalyst comprised of molybdenum oxide finely dispersed in silica or of both molybdenum oxide and titanium oxide finely dispersed in silica has described. The major issue with this catalyst is its deactivation in recyclability studies. The activity of the catalyst drops down from 92 to 20% in the fifth run. The metal content leaches into the reaction medium during the runs. Therefore, a more selective and stable catalyst system even for applications to polyenic fatty acid esters is highly desirable.
References may be made to U.S. Pat. No. 3,634,464, wherein a process of epoxidizing an olefinically unsaturated organic compound with an organic hydroperoxide such as tertiary substituted and unsubstituted-hydrocarbon hydroperoxide e.g. tertiary butyl hydroperoxide, in the presence of a catalyst composition comprising an oxide of molybdenum and a solid inorganic oxide catalyst support containing a major proportion of at least one oxide component selected from silica and alumina, modified by the inclusion therewith of bismuth or certain rare earth metal oxides, said catalyst composition incorporating from about 0.1% to 10% by weight of bismuth or rare earth metal oxide. The catalyst composition is characterized by being essentially insoluble in the epoxidation reaction mixture, providing a heterogenous system has reported. Molybdenum oxide is present in amounts from 0.2% by weight to 5% by weight calculated as molybdenum on the catalyst support. A critical feature of catalyst composition is the presence of a minor proportion of bismuth or certain rare earth oxides as catalyst modifier. It is evident that the modifier plays a substantial role in providing a heterogenous catalyst composition wherein the oxide of molybdenum is not dissolved in the epoxidation reaction mixture, thereby eliminating the requirement of additional apparatus and separation steps for recovery of any soluble molybdenum. Suitable rare earth metal oxide modifiers are oxides of metals having atomic numbers 57 to 71 inclusive, i.e. the lanthanides. Among the oxygen-containing substituted-hydrocarbon olefins which are suitably epoxidized by the process of the invention includes olefinically unsaturated carboxylic acids such as crotonic acid, oleic acid and tetrahydrobenzoic acid; oxygen containing compounds such as soybean oil and corn oil etc. The epoxidation process is conducted at a temperature varying from about 0° C. to about 200° C., preferably from 25 to 200° C., at or above atmospheric pressure, varying from about 1 to 100 atm.
References may be made to Bulletin of the Chemical Society of Japan; Year 1986, Vol. 59, No. 12, pp. 3941-3943, wherein Yasushi Itoi et al. disclose epoxidation of fatty acid esters with 30% aqueous hydrogen peroxide in the presence of a molybdenum oxide-tributyltin chloride on a charcoal catalyst in 2-propanol at 50° C. Such inner olefins as ethyl erucate and ethyl oleate gave yields of 77% and 76%, respectively. Ethyl elaidate, a trans-form of ethyl oleate, was found less reactive (40% yield).
References may be made to Journal “Applied Catalysis A: General Year 2003, Vol. 248, pp. 261-268” and “U.S. Pat. No. 3,351,635”, wherein said references disclose the application of homogeneous molybdenum catalysts but then catalyst separation and reuse are issues with those catalyst systems.
In view of the above it is desirable to have an improved, more efficient, selective and reusable solid-catalyst and a process beneficial from environment and economic viewpoints. The process of the present invention using supported molybdenum oxide solid catalyst has all the above-mentioned desirables.